Antenna mast misalignment detector

ABSTRACT

An antenna misalignment detector has two electrolytic transducers mounted on a mast carrying the antenna perpendicular to each other in the same horizontal plane. The antenna is mounted on a mast. The square root of the sum of the squares of the output from the transducers is generated and compared with a predetermined reference so that an alarm sounds when the antenna is misaligned along a vertical axis to the ground.

United States Patent 1191 Talkington et al.

ANTENNA MAST MISALIGNMENT DETECTOR [75] Inventors: Carl M. Talkington; Hamil W. Cooper, both of Austin, Tex.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: June 7, 1971 [21] Appl. No.: 150,490

[52] US. Cl 340/213 R, 33/366, 340/261 [51] Int. Cl. G08b 21/00 [58] Field of Search 340/213, 261, 282,

[56] I References Cited UNITED STATES PATENTS 3,096,591 7/1963 Higgins, Jr. et 340/200 X 1 June 12, 1973 12/1964 Bianchi et a1 328/148 x 3,159,825 3,317,648 5/1967 Pollack 235/1935 X 3,631,469 12/1971 Levy 340/178X Primary Examiner-Donald J. Yusko Attorney-James 0. Dixon, Andrew M. .Hassell, Harold Levine, Renee E. Grossman and James T. Comfort [57] ABSTRACT An antenna misalignment detector has two electrolytic transducers mounted on a mast carrying the antenna perpendicular to each other in the same horizontal plane. The antenna is mounted on a mast. The square root of the sum of the squares of the output from the transducers is generated and compared with a predetermined reference so that an alarm sounds when the antenna is misaligned along a vertical axis to the ground. 1

3 Claims, 3 Drawing Figures nrrsmsnce ssuennon 55 SENSOR season 120 vac raaus- *so' FORMER POWER SUPPLY Patented June 12, 1913 3,739,364

2 Sheets-Sheet 1 [j If! Fig.2

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INVENTOI? CvnT ATTORNEY ANTENNA MAST MISALIGNMENT DETECTOR This invention is directed to an antenna mast misalignment detector. 7

It is important to maintain the vertical alignment of a mast carrying an antenna at the proper vertical alignment to allow correct operation of the antenna. There have been previous misalignment detectors applied to antenna masts to detect a misalignment. One of the simplest approaches has been to use a plurality of mercury switches. These switches are available with sensitivity on the order of minutes. A number of these switches have been mounted on a circular plate with a DC voltage applied to them. However, it is fairly hard to adjust this arrangement to the accuracy which is required, and it is fairly expensive. Also, decreased temperature increases the density of the mercury and makes the trip points of the switches uncertain.

, Another approach has been to use a bubble of oil and sense its position with a light sensitive photocell. However, there is a variation in oil density with a change in 2 temperature. Such a system is also difficult to adjust and'is mechanically complex. Another approach has been to use a pendulum with light sensitive photocell. This approach is also mechanically complex and expensive.

Misalignment detectors are necessarily in an accessible place so that they could be easily adjusted, and once adjusted, maintain their adjustment. The operating temperature range is approximately -54 to +71C and there must be a sensitivity to an angular deflection of 30 minutes.

It is therefore an object of this invention to provide a new and improved misalignment detector for antennae.

It is another object of this invention to provide a new and improved misalignment detector for antennae which is inexpensive and accurate.

Referring now to FIG. 1, the top of a vertical mast 21 is shown with an antenna 23 attached thereto. Only a portion of the mast is shown. The mast itself is a tripod with only two pieces 25 and 27 of the tripod shown with bracing members 29. A top plate 31 is secured to the top of the mast 21. Misalignment detector 33 is secured to the top plate 31 by three adjustable screws of which two screws 35 and 37 are shown. An obstruction light .39 is shown on the top of the top plate 31.

FIG. 2 shows the misalignment detector 33 on the misalignment detector plate 32. The misalignment detector plate 32 is attached to the'top plate 31 shown in FIG. 1 by the three adjustable screws 35, 36 and 37. The adjustment screw 37 is a fixed pivotpoint while the adjustment screw 35 adjusts the misalignment plate 32 along the X-axis and the adjustment screw 36 adjusts the misalignment plate 32 along the Y-axis. The misalignment detector 33 itself contains a first electrolytic transducer 41 along the X-axis and the second electrolytic transducer 43 along the Y-axis. The electrolytic transducers 41 and 43 are showii in FIG. 2 although they are actually contained inside the misalignment detector box 33. There is an X-axis test jack 45 to test the alignment of the X-axis electrolytic transducer 41 and a Y-axis test jack 47 to test the alignment of the Y-axis electrolytic transducer 43 along the Y-axis. There is a ground-test jack 49. There is also a connector output 51. To properly adjust the misalignment detector 33 along the X-axis, the X-axis electrolytic transducer 41 is tested through the X-axis output test jack and the adjusting screw 35 is adjusted until the electrolytic transducer 41 indicates even alignment. The same procedure is followed to align the Y-axis electrolytic transducer. i

The electrolytic transducers are manufactured by Hamlin Corporation. These units require AC voltage. The two electrolytic transducers are mounted on a perpendicular axis to each other on the flat plate in the misalignment detector 33.

The analog output of the devices, each of which is proportional to the angle of tilt along the axis on which it ismounted, is taken and a square root of the sum of the squares approximation is made. The following approximation is implemented:

[cos 0 I A: l' sine6|= l taking the derivative and setting equal to 0 df(6)/d0 O sin6d6 cosOdO 0 sin@ VzCOSB tan0 0.5

sin6 0.446

cos6 0.895

118 is the maximum value, the minimum value of the function is l. The maximum error is therefore 0.118.

If the true value of the function is taken halfway between and the approximation introduces an error of about +5 percent or .-5 percent, this gives a good approximation of the circular pattern with little discrep-- ancy between an off-axis and an on-axis tilt.

Referring now to FIG. 3, a transformer provides a low voltage to the power supply 53 for use by the circuitry. Another output from the transformer 55 is applied to a reference generator 57 and to the two electrolytic transducers 41 and 43. The output from the transformer is also applied through resistors 61-64 to each end of the electrolytic transducers 41 and 43. The

output from electrolytic transducer 41 isapplied to differential amplifier 67 and to summing amplifier 69. The

77. The output from the summing amplifiers and 77 is applied to the IF stage 79 to OR- circuit 81.

The reference generator generates a predetermined voltage which is applied through adjustable resistors 83 and 85 to an IF stage 87 and through an adjustable resistor 89 to the IF state 79. The output from summing amplifier 69 is applied to the input of IF stage 87. The output from IF stage 87 is applied to one input of OR circuit 81. The output from OR circuit 81 is applied to delay circuit 90 and to an alarm circuit 91.

This circuitry shown in FIG. 3 generates a sum of all voltages on the transducers 41 and 43. Since the normal condition is a null, a transducer malfunction is detected by requiring that the sum of: the voltages be between two Iimits. It also generates the approximation for the square root of the sum of the squares of the voltages on transducers 41 and 43. An alarm is then generated if this voltage exceeds the set reference. The time delay is included so the vibrations and other temporary disturbances do not set off the alarm.

This circuitry detects misalignment on the X- and Y- axes and all points between. The time delay may be adjustable, for instance between 30 seconds and 4 minutes.

The gravity sensing electrolytic transducer is-a device designed to provide an output voltage having a magnitude proportional to tilt angle indicative of tilt direction when connected in a bridge circuit and excited with an AC voltage. The sensor consists of an electrolytic fluid enclosed in a glass envelope. The envelope contains three electrodes in contact with theelectrolytic fluid. When the sensor is tilted, the impedance between two of the terminals increases, while the impedance between the other two decreases. When connected in a bridge arrangement, a differential AC voltage will be obtained.

What is claimed-is:

1. An antenna misalignment detector comprising:

a first electrolytic transducer mounted on a first axis,

a second electrolytic transducer mounted on a second a-xis perpendicular to said first axis,

means for setting a predetermined reference,

means responsive to said first and second electrolytic transducers for generating the square root of the sum of the squares of the voltages of said transducers, and

means for comparing said generated signal and said reference to detect an antenna misalignment.

2. An antenna misalignment detector comprising:

an antenna,

a first electrolytic transducer having an output signal proportional to its angle of tilt along its axis mounted on said antenna along a first axis,

a second electrolytic transducer having an output signal proportional to its angle of tilt along its axis mounted on said antenna along a second axis perpendicular to said first axis,

means responsive to the output signals from said first and second transducers for generating the square root of the sum of the squares of the signals of said transducers,

means for setting a predetermined reference, and

means for generating an alarm when said generated square root exceeds said set reference. 3. The antenna misalignment detector claimed in claim 2 including a delay means to delay said alarm for a predetermined period of time.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3, 739 364 DATED 1 June 12, 1973 |NvENT0R(S) 1 CARL M. TALKINGTON; HAMIL w. COOPER It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: I

In the first paragraph of the specification the following sentence is inserted -The invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Air Force.

Signed and Scaled this First Day Of November 1977 [SEAL] Attest:

RUTH C. MASON LUTRELLE F. PARKER Attesting Officer Acting Commissioner of Patents and Trademarks 

1. An antenna misalignment detector comprising: a first electrolytic transducer mounted on a first axis, a second electrolytic transducer mounted on a second axis perpendicular to said first axis, means for setting a predetermined reference, means responsive to said first and second electrolytic transducers for generating the square root of the sum of the squares of the voltages of said transducers, and means for comparing said generated signal and said reference to detect an antenna misalignment.
 2. An antenna misalignment detector comprising: an antenna, a first electrolytic transducer having an output signal proportional to its angle of tilt along its axis mounted on said antenna along a first axis, a second electrolytic transducer having an output signal proportional to its angle of tilt along its axis mounted on said antenna along a second axis perpendicular to said first axis, means responsive to the output signals from said first and second transducers for generating the square root of the sum of the squares of the signals of said transducers, means for setting a predetermined reference, and means for generating an alarm when said generated square root exceeds said set reference.
 3. The antenna misalignment detector claimed in claim 2 including a delay means to delay said alarm for a predetermined period of time. 